this , that , (this pronoun is enclitic and cannot begin a sentence ; it is generally used alone , so that [ enam puruṣam ] , " that man " , would be very unusual if not incorrect. Grammarians assert that the substitution of [ enam ] for [ imam ] or [ etam ] takes place when something is referred to which has already been mentioned in a previous part of the sentence ; see Gr. 223 and 836)